The present invention relates to database systems, and more specifically, to compression and decompression techniques for use in database systems. Database systems manage large amounts of data, and commonly use data compression as a means to reduce the amount of disk and/or memory storage used to house data objects.
For example, the DB2 database system, which is available from International Business Machines Corporation of Armonk, NY, offers a storage optimization feature, which uses a combination of compression features that transparently compresses data on disk in order to decrease disk space and storage infrastructure requirements. Since disk storage systems can often be the most expensive components of a database solution, even a small reduction in the storage subsystem can result in substantial cost savings for the entire database solution. Some of the data compression techniques used in the DB2 database system include Row Compression, Adaptive Row Compression, and XML Compression.
While the various compression techniques typically provide substantial savings in memory and storage use, they also incur greater use of Central Processing Unit (CPU) resources (i.e. higher CPU use) when accessing the data. Therefore, it would be advantageous to have techniques that reduce the amount of CPU resources that are needed when only a portion of the compressed data needs to be accessed.